Nitrocellulose propellent powder



Patented Apr. 19, 1932 are ever Ltdtjlt RICHARD GEORGE WOODBRIDGE, OFWILMINGTON, DELAWARE, ASSIGNOR T0 E. I. DU PONT DE NEMOURS & CQMPANY, OFWILMINGTON, DELAWARE, A. CORPORATION OF DELAWARE IiTITROCELLULOSEPROPELLENT POWDER No Drawing.

This invention relates to nitrocellulose propellent powder havingcertain advantageous properties, and to a process of making such powder.

This application is a continuation as to common subject matter of mycopending application Serial No. 81,086, filed January 13, 1926.

The object of my invention is to produce a smokeless propellent powderfrom nitrocellulose without the aid of nitroglycerine which will possessgreatly reduced hygroscopic qualities as compared with a powder madefrom nitrocellulose only. A further object of my invention is theelimination of the white luminous flash such as is produced at themuzzle of guns by the present pyro service powder of the United StatesGovernment. This white luminous muzzle flash is commonly attributed tothe ignition of the combustible gases formed during the combustion ofsmokeless powder, due to their high temperature when emerging from themuzzle of the gun and coming in contact with the oxygen of the air. Thegaseous products formed by the combustion of smokeless powder arenitrogen, carbon dioxide, carbon monoxide, hydrogen, water vapor andsmall amounts of methane. Of these the combustible gases are carbonmonoxide, hydrogen and methane. The white luminous flash at the muzzleof the gun is due to the combustion of these latter gases in thepresence of oxygen. This combustion can be prevented in the case ofsmall arms by firing into an atmosphere of carbon dioxide. When thewhite luminous flash is eliminated in this manner, or is eliminated bythe use of a powder containing suitable ingredients, only a smallreddish glow appears at the muzzle of the gun upon firing. This glow isnot readily visible and can be easily concealed.

A further object of my invention is the production of a nitrocellulosepropellent Application filed February 13, 1931. Serial No. 515,642.

powder which, besides being of greatly reduced hygroscopicity andflashless in most guns, contains no water soluble ingredients aside fromthe volatile solvents, ether and ethyl alcohol, which may be used in themanufacture, and therefore can be dried not only in air but also in hotwater to more effectively and expeditiously remove the volatile solventsadded for the purpose of assisting in the colloiding of thenitrocellulose.

The hygroscopicity of a nitrocellulose propellent powder is a factorlargely of the amount, and nitrogen content, of the nitrocellulose used.For example, nitrocellulose of 12.60% nitrogen content will containabout 2.00% moisture when in equilibrium with 70% relative humidity at30 C. A nitrocellulose of 13.15% nitrogen will contain about 1.5%moisture under the same conditions. Colloiding the nitrocellulose withether and alcohol has but little effect on the hygroscopicity of thenitrocellulose in the small rifle powder grains and even in powdergrains suitable for the 75 m/m field gun, but there is a gradualreduction in hygroscopicity as the size of the powder grains isincreased or, in other words, as the amount of residual solvent etherand alcohol left in the powder is increased.

I have found that certain classes of organic compounds are particularlysuitable for the double purpose of reducing the hygroscopicity of thenitrocellulose and eliminating the luminous white muzzle flash at thesame time. The compounds which I have found especially suitable aredibutylphthalate, diethylphthalate, dibutyltartrate, ethyl palmitate,acetyllaurins, etc. These compounds possess the desirable properties ofbeing good solvents for nitrocellulose, liquid at ordinary temperature,of relatively low volatility, especially when colloided withnitrocellulose; besides being substantially insoluble in water andsubstantially non-hygroscopic. These compounds are further characterizedby being deterrent materials of a non-explosive character, containing arelatively small percentage of oxygen and a relatively high percentageof carbon and hydrogen.

I have further found that the quantity of the above compounds requiredto eliminate the muzzle flash of a nitrocellulose propellant isrelatively small, so that when used alone with nitrocellulose thequantity required to produce flashlessness, particularly in the smallerguns, would be insuflicient to have much effect on reducing thehygroscopicity of the nitrocellulose.

I have further discovered that in order to produce a nitrocellulosepropellent powder which will have greatly reduced hygroscopicity ascompared with, for example, the present pyro powder of the United StatesGovernment and at the same time be flashless in many guns, it isdesirable to substitute for a portion of the nitrocellulose, in additionto the portion substituted by the flash eliminating compound, asubstantially non-hygroscopic and water insoluble nitro-aromaticcompound which when liquid has a substantial solvent action on thenitrocellulose.

As an example of a nitro-aromatic compound which answers my purpose Imay mention dinitrotoluene. While ordinary 1-2-4 dinitrotoluene is asolid and as such has no water-proofing-a-ctionon the nitrocellulose, Isubject the powder composition containing dinitrotoluene, at some stageof its manufacture, to a temperature suflicient in the presence of aflash reducing ingredient such as dibutylphthalate to cause the mixtureto melt. As both dinitrotoluene and dibutylphthalate, either alone or inmixture, are excellent solvents for nitrocellulose, there is obtained athorough colloiding of the nitrocellulose by the mixture, resulting in asubstantial reduction in the hygroscopicity of the nitrocellulose. Thisreduction is greater thanthe reduction due to simply substituting aportion of the nitrocellulose by an equal portion of the aboveingredients, and is due to a depression of the hygroscopic qualities ofthe nitrocellulose by the colloiding action of the mixture ofnon-volatile solvents.

My invention may therefore be said to comprise, as one importantfeature, the combination of a nitro-aromatic compound with a flasheliminating compound, both of which are substantially water insolubleand nonhygroscopic and both of which are substantial solvents, alone orinadmixture, for nitrocellulose. The substitution of a substantialportion of nitrocellulose by these two ingredients, in addition to theso-called water-proofing effect of the ingredients themselves on thenitrocellulose, produces a nitrocellulose propellent powder of greatlyreduced hygroscopicity and flashless in many guns.

I do not wish to be understood as asserting that propellent powders madein accordance with my invention are non-hygroscopic, as it has been myexperience that all powders, whether of the nitrocellulose orof thenitroglycerine type, possess a definite degree of hygroscopicity.Furthermore, the hygroscopicities of propellent powders made inaccordance with my invention areyery .much lower than those of the usualtype of nitrocellulose powders. As proof of the above I present thefollowing hygroscopic tests made by exposing powders of the compositionsas shown to a relative humidity of at a temperature of 30 C. untilequilibrium was reached.

Composition, exclusive of stabilizer Nitrocellulose oi Dinitro- Dlbutyl-13.15% N. toluene phthalate 100% None. None. 95% None. 5% None. 10% 85%None. 15% 30% None. m Y 5% None. 90% i0 None. 85% .15 0 None. 80% 20%None. 12 80% 0% 0% 13 %py1-o of 12.60% N. None None of these ingredientswith 85 parts nitrocellulose without the disadvantage of using 15 partsof either ingredient.

The same advantage as regards hygroscopicity and elimination of flashmay be obtained by substituting'for the dibutylphthalate many otherdeterrent non-volatile solvents for nitrocellulose To illustrate" thispoint I give the results of ballistic test-in the 7 5 m/m field gunmodel of 1897 usingthe 13 pound projectile of powders of variouscompositions, together with the results of hygroscopic tests at 70% Irelative humidity at 30 C.':

III

Composition 1 I fi i Lumi- Weight p c nous Dinitrotoluene or 1 chiiige$533; vigil) liiiiz iie 1.315% substitute Flash eliminating ingredientlpgnrdty flash V 0 Feet p51- Lbs 1g u'ncea seco'n sq. m 85% 10% DNT 5%dibut lphthalate 28 1956 35950 0.77% None 85% 107 DNT 5% dimetyldiphenyluroa 27% 1945 35810 0.78% None 85% 10 a DNT 5% acetyl laurins28% 1947 32280 0.76% N 0116 85% 10% DN T 5% ethyl palmitate 30 194930600 0. 82% None DN T d et y p t 27% 1949 33510 0. 69% None 85 DNT 5%dibu yltartrate 27 1925 31900 0.70% None 85 a 10% trinitrotoluene 5%dibutylphthalate 27 1952 35770 0.76% None 1 34% added diphenylamine as astabilizer. a

oisture determined by heatinc 6 hours in vacuum oven at 50-60 C.

In place of dimethyldiphenylurea, diethyldiphenylurea ormethylethyl-diphenylurea may be used.

With the exception of the dimet-hyldiphenylurea, diethyldiphenylurea andmethylethyld'iphenylurea, all of the above flash eliminating ingredientsare liquid. They are also excellent solvents for nitrocellulose. Whiletetra substituted urea compounds are solid, when mixed with thedinitrotoluene mixtures can be obtained melting below 80 C. that is, ata temperature Well within suitable limits for safe manufacture,especially when the powder is subjected towater drying treatment afterthe removal of volatile solvents. It should, therefore, be understoodthat either or both the nitro-aromatic compound and the flasheliminating 'ingredient may be solid provided that a mixture of the twowill melt below a temperature of about 80 C. and thus colloid thenitrocellulose by reason of their combined solvent action on the same.

I have found that no single composition will give fiashless results inall types of guns. In some guns, due to relatively short barrel andrelatively severe ballistic requirements, it is often impossible toobtain flashless results with a powder which may give fiashless resultsin some other gun. Furthermore, that the manner in which the powder isignited, the quantity and arrangement of the supplementary black powderignition charge are all of great importance in some guns in connectionwith obtaining fiashless results. I have further found that in some gunsthe type of powder grain is of importance, and that the strip type ofpowder grain appears to give better results in some guns than themultior single perforated.

I have further found that the chemical stability of powder made inaccordance with my invention, for example from nitrocellulose,dinitrotoluene, dibutylphthalate and diphenylamine, is far greater thanthat of powder made from nitrocellulose and diphenylamine only; this Iattribute as being due to the thorough colloiding of the nitrocelluloseby the mixture of dinitrotoluene and dibutylphthalate used and thesolution of the diphenylamine in the latter mixture.

Nitrocellulose of relatively high nitrogen is preferred in order toobtain the advantage of the lower hygroscopicity possessed bynitrocellulose of high nitrogen content. I no not limit myself to theuse of nitrocellulose with a nitrogen content of 13.15% which has beenpreviously set. forth in certain examples as purely illustrative. Itwill be apparent from the foregoing that I can use nitrocellulose ofmuch higher nitrogen content, for example as high as 13.50, or evenhigher, and in conjunction therewith increased or decreased amounts ofdinitrotolucne and dibutylphthalate depending on the ballistic andchemical qualities desired and whether or not flashless results aredesired. I, therefore, do not limit myself as regards the maximumnitrogen content of the nitrocellulose. It will also be apparent that Ican use nitrocellulose of lower nitrogen content than 13.15% withvarious amounts of dinitrotoluene and dibutylphthalate, but asnitrocellulose of lower nitrogen content is more hygroscopic and of lesspotential than nitrocellulose of higher nitrogen content, I prefer touse nitrocellulose with nitrogen content in excess of 12.85%. Asindicated in the foregoing, I can use nitrocellulose having a nitrogencontent-greater than 13.50, but heretofore nitrations other than bylaboratory methods have not produced a product having satisfactorystability. While I may use more than 10% of the nitro-aromatic compound,such as dinitrotoluene, in the composition, I have found that thisamount is very satisfactory to give with nitrocellulose of about 13.15%nitrogen content and 215% of dibutylphthalate, a propellent powderpossessing requisite potential for present type of ordnance. When asmuch as 5% of dibutylphthalate is used, no muzzle flash is obtained inmany of the smaller guns. For example, flashless results are obtainedwith a powder of the composition85 parts nitrocellulose of about 13.15%nitrogen, 10 parts dinitrotoluol, 5 parts dibutylphthalate and 1%diphenylamine when fired in the 7 5 mm. French field gun model 1897,with the 13% pound projectile at the usual muzzle new velocity of 1955feet per second. For this articular gun and projectile the amount ofibutylphthalate may be reduced to i parts, the nitrocellulose contentbeing increased to 86 parts and flashless results still be obtained.However, it is preferable to use 5 parts of dibutylphthalate whenflashless results are desired in this gun because of providing greatermargin of safety as regards fiashlessness.

In some guns fiashless results may be obtained by increasing the amountof dibutylphthalate as illustrated by the following com-' positions:

Nitrocellulose of t 1 mm Di he 1 high nitrogen Dinitrotoluene l u y p ap content late amine parts 10 parts 7 parts lpart .82 parts 10 parts 8parts 1 part 80 parts "I 10 parts 10 parts 1 part However, the use oftoo much. dibutyl late and 1 part diphenylamine and are preferred foruse in a number of guns where flashless results are either not desiredor where fiashlessness is a secondary conideration to other properties.For example, a powder of the composition 87 parts of nitrocellulose of13.15% nitrogen, 10 parts dinitrotoluene, 3 parts of dibutylphthalateand 1 part of diphenylamine gives very satisfactory ballistic results inthe larger guns, particularly on account of slightly increased potentialand is also entirely suitable for use in smaller guns wherefiashlessness is not desired, although in some of the smaller guns thiscomposition gives flashless results.

The manufacture of the powder requires no special skill. Thenitrocellulose is dehydrated with denatured ethyl alcohol of suitablegrade and then colloided. in a suitable mixer with the addition ofether. There is added in the ether or directly to the mixer, thedinitrotoluene and the dibutylphthalate. Due to the solvent action ofthe latter two ingredients, the amount of ether and alcohol required issomewhat less than usually used for nitrocellulose powders notcontaining these ingredients. Acetone may be used to replace all or partof the ether. DiphenyL amine is usually added as a stabilizer and isusually dissolved in the ether. The colloid may be pressed either incylindrical grains with one or more perforations or withoutperforations, or in the ribbon or strip form of grain or any other kind.

The grains of powder aregiven thorough perature maybe used withoutinjury to thechemical sta lity of the powder.

As many. apparetnly widely different embodiments of this invention maybe made without departing from the spirit thereof, it is to beunderstood that I do not limit myself.

to the foregoing examples'or descriptions except as indicated in thefollowing patent claims:

I claim:

1. A ropellent powder, capable of being water 'ried, comprisingnitrocellulose incorporated with a deterrent explosive'andaflash-eliminant ingredient, each of which when in liquid form has asubstantial solvent action on the nitrocellulose the deterrent explosivebeing present in greater amount than the flash-eliminant ingredient.

2. A propellent powder, capable of being Water dried, comprislngnitrocellulose incorporated with a nitro-aromatic compound'and aflash-eliminant ingredient, each of which when in liquid form has asubstantial solvent action on the nitrocellulose the deterrent explosivebeing present in greater amountthan the flash-eliminant ingredient.

3. A propellent powder, capable of being water dried, comprisingnitrocellulose incorporated with a nitro-aromatic compound and aflash-eliminant ingredient, each of which when in liquid form has asubstantial solvent action on the nitrocellulose, and each of which issubstantially insoluble in water, the-deterrent explosive being presentin greater amount than the fiash-eliminant ingredient.

4. A propellent powder, capable of being.

water dried, containing nitrocellulose, a polynitrotoluene, and adialkyl phthalate.

5. A propellent powder, capable of being water dried, comprisingnitrocellulose, an organic nitro-compound other than nitrocellu-v losewhich is substantially non-hygroscopic and water-insoluble and whichwhen in liquid form has a substantial solvent action on nitrocellulose,and an alkyl ester of an organic acid, said ester havingflash-eliminating properties and being further characterized by havinginliquid form a substantial solvent action on nitrocellulose, a lowvolatility when colloided with nitrocellulose, and

by being substantially insoluble in water, and

substantially non-hygroscopic;

6. A propellent powder, capable of being water dried, comprisingnitrocellulose having incorporated therein a nitro-aromatic compound,and a flash-eliminant in .;.l30

cut, the nitroaromatic compound and the water dried, containingnitrocellulose, dini- 10. A nitrocellulose trotoluene and dibutylphthalate.

9. A propellent powder, capable of being water dried, containingnitrocellulose, dinitrotoluene, dibutyl phthalate and diphenylamine.

propellent powder,

I the hygroscopicity of which is depressed below that of thenitrocellulose itself by a mixture incorporated therein of anitro-aromatic compound and a flash-eliminant ingredient, both of whichwhen liquid have substantial solvent action on the nitrocellulose, thenitroaromatic compound being present in greater amount than theflash-eliminant ingredient.

11. A propellent powder as defined in claim 1 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

12. A propellent powder as defined in claim 2 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

13. A propellent powder as defined in claim 3 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

14. A propellent powder as defined in claim 4 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

15. A propellent powder as defined in claim 5 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

16. A propellent powder as defined in claim 6 in which at least asubstantial part of the nitrocellulose has a nitrogen content of 12.85per cent to 13.50 per cent.

17. A propellent powder capable of being water dried, containingnitrocellulose, in combination with a flash eliminant taken from a groupconsisting of dibutyl phthalate. diethyl phthalate, dibutyl tartrate,ethyl palmitate, and acetyl-laurin, in which at least a substantial partof the nitrocellulose has a nitrogen content of 12.85 per cent to 13.50per cent. I

18. A propellent powder as defined in claim 1 in which at least asubstantial part of the nitrocellulose .has a nitrogen content of from13.05 per cent to 13.25 per cent.

A propellent powder as defined in claim 2 in which at least asubstantial part of the nitrocellulose has a nitrogen content of from13.05 per cent to 13.25 per cent.

20. A propellent powder as defined in claim 3 in which at least asubstantial part of the nitrocellulose has a nitrogen content of from13.05 to 13.25 per cent.

21. A propellent powder as defined in claim 4 in which at lease-asubstantial part of the nitrocellulose has a nitrogen content of from13.05 to 13.25 per cent.

22. A propellent powder as defined in claim .5 in which at least asubstantial part of the nitrocellulose has a nitrogen content of from.13.05 to 13.25 per cent.

23. A propellent powder as defined in claim 6 in which at least asubstantial part of the nitrocellulose has a nitrogen content of from-13.05 to 13.25 per cent.

24. A propellent powder as defined in claim 1 in which at-least asubstantial part of the nitrocellulose hasa nitrogen content greaterthan 12.85 percent.

25. A propellent powder as defined in claim 2 in which'at least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85 per cent.

26. A propellent powder as defined in claim 3 in which at least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85per cent. 7

27. A propellent powder as defined in claim 4 in which as least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85 per cent.

28. A propellent powder as defined in claim 5 in which at least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85 per cent.

29. A propellent powder as defined in claim 6 in which at least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85 per cent.

30. A propellent powder capable of being water dried, containingnitrocellulose, in combination with a flash eliminant taken from a groupconsisting of dibutyl phthalate, diethyl phtllalate, dibutyl tartrate,ethyl palmitate, and acetyl-laurin, in which at least a substantial partof the nitrocellulose has a nitrogen content of from 12.85 per cent to13.35 per cent.

31. A propellent powder capable of being water dried. containingnitrocellulose, incorporated with a flash eliminant taken from a groupconsisting of dimethyldiphenylurea, diethyldiphenylurea, phenylurea.

32. A propellent powder, capable of being water dried, containingnitrocellulose, having incorporated therein dinitrotoluene, and a memberof a group consisting of dimethyland methylethyldidiphenylurea,diethyldiphenylurea and methylethyldiphenylurea, as a flash ehmlnant,the dinitrotoluene being present in greater quantity than theflash-eliminant ingredient.

33. A propellent powder caplable of being water dried, contaimng nitroceulose, having incorporated therein dinitrotoluene, and a flash-eliminanttaken from a group consisting of dimethyldiphenylurea,diethyldiphenylnrea and methylethyldiphenylurea, in least a substantialpart of the nitrowhich at cellulose has a nitrogen content of 12.85 percent to 13.50 per cent, the dinitrotoluene being present in greaterqauntity than the flasheliminant ingredient.

34. A propellent powder capable of being water dried, containingnitrocellulose, having incorporated therein dinitrotoluene, and aflash-eliminant taken from a group consisting of dimethyldiphenylurea,diethyldiphenylurea and methylethyldiphenylurea, in which at least asubstantial part of the nitrocellulose has a nitrogen content of 13.05per centto 13.25 per cent, the dinitrotoluene being present in greaterquantity than the flasheliminant ingredient.

35. A propellent powder capable of being water dried, containingnitrocellulose, having incoporated therein dinitrotoluene, and afiash-eliminant taken from a group consisting of dimethyldiphenylurea,diethyldiphenylurea and methylethyldiphenylurea, in which at least asubstantial part of the nitrocellulose has a nitrogen content greaterthan 12.85 per cent, the dinitrotoluene being present in greaterquantity than the flash-eliminant ingredient.

36. A nitrocellulose propellent powder containing nitrocellulose,dinitrotoluene and dibutylphalate, and having a hygroscopicity at arelative humidity of 7 0 per cent and. at a temperature of 30 C. below 1per cent.

In testimony whereof, I afiix my signature.

. RlCHARD GEORGE WOODBRIDGE.

